A belt of the abovementioned type plays a prominent part in drive technology in particular. Such belts, which are also known as drive belts or power transmission belts, can be configured as flat belts, V-belts, V-ribbed belts, toothed belts or as composite cables. The power transmission zone corresponds to the belt drive. The following patent literature in particular is referenced in this regard: DE 38 23 157 A1; U.S. Pat. No. 7,128,674; U.S. Pat. No. 8,262,523; DE 10 2007 062 285 A1; DE 10 2008 012 044 A1; DE 10 2009 044 153 A1; U.S. Pat. No. 5,807,194; WO 2005/080821 A1; US 2008/0032837; US 2011/0129647; U.S. Pat. No. 3,981,206; U.S. Pat. No. 5,417,618; and, U.S. Pat. No. 6,491,598.
It is further known to use belts to convey materials, belts of this type also being referred to as transport belts or conveyor belts. The top ply serving as belt backing here would then be the carrying-side cover in contact with the conveyed material. The substructure would then in turn be the return-side cover, which is in contact with a driving drum.
An elastic belt is elastic because the belt body and thus the top ply and the substructure comprise a polymeric material having elastic properties, suitable materials here being in particular the two groups known as elastomers and thermoplastic elastomers. Elastomers based on a crosslinked mixture of rubber are particularly important, the mixture containing at least a rubber component and mixture ingredients. The rubber component used is more particularly ethylene-propylene rubber (EPM), ethylene-propylene-diene monomer rubber (EPDM), (partially) hydrogenated nitrile rubber (HNBR), fluoro rubber (FKM), natural rubber (NR), chloroprene rubber (CR), styrene-butadiene rubber (SBR), butadiene rubber (BR) or polyurethane (PU), which are cut with at least a further rubber component, in particular with one of the aforementioned types of rubber, for example in the form of an EPM/EPDM or SBR/BR blend, or uncut. HNBR, EPM, EPDM, PU or an EPM/EPDM blend are particularly important here. The mixture ingredients comprise at least a crosslinker or crosslinker system (crosslinking agent plus accelerant). Further mixture ingredients are usually also a filler and/or a processing aid and/or a plasticizer and/or an antioxidant and also optionally further added substances, for example fibers for reinforcement and color pigments. The general rubber-mixing arts are referenced in this regard.
The belt comprises an embedded tensile member which is formed of at least a tensile strand extending in belt longitudinal direction. Usually, two or more tensile strands combine to form a tensile member ply. Particular importance attaches here to a tensile strand in cord construction, for which various materials are possible according to the prior art. The preferred types of material are: steel, polyamide (PA), aramid, polyester, carbon, basalt, polyetheretherketone (PEEK), polyethylene terephthalate (PET), polybenzoxazole (PBO) or polyethylene 2,6-naphthalate (PEN).
Especially the power transmission zone of a belt for drive technology is endowed with an abrasion-resistant coating which additionally serves as a noise reducer and may also be rendered oil resistant. What is used for this purpose is a flocked add-on ply, in particular in the form of a cotton or aramid flock, a thin elastic polymeric layer filled with fibers (e.g., aramid fibers), a textile add-on ply, in particular in the form of a woven or knitted fabric, or a self-supporting film or sheet (e.g., a PTFE film or sheet) or a composite film or sheet (e.g., a PA-PTFE film or sheet). The woven fabric is of particular importance. The coatings recited here are usually treated on the contact side to the belt body, in particular to the substructure thereof, in an adherence-promoting manner, for example with a resorcinol-formaldehyde latex (RFL).
The prior art of polyurethane treatment of the tensile member will now be reviewed in more detail.                U.S. Pat. No. 5,807,194 discloses a toothed belt wherein the belt body includes a cast polyurethane. The embedded tensile member in cord construction is formed of carbon fibers together with a cord treatment. As the belt is cast, only some of the tensile member voids become filled with the cast polyurethane material. The disadvantage is that such a treatment of the tensile member with polyurethane is predicated on the fact that the belt body should likewise consist of a polyurethane of the same composition. No regard is accordingly had to the different properties of the carbon-type tensile member and of the belt body.        US 2011/0129647, then, discloses a belt, in particular a toothed belt and a V-ribbed belt, whose tensile member in cord construction, in particular carbon-type tensile member, has been treated with a crosslinked polyurethane. The fillage of the tensile member voids with the crosslinked polyurethane is preferably in the range from 20% to 100%. The polyurethane is further preferably formed from the following components A and B in particular:                    component A: polyols selected from polyester polyols, polycarbonate polyols and polyether polyols;            component B: diisocyanates, in particular para-phenylene diisocyanate and 4,4′-methylenediphenyl diisocyanate.                        
A polyol is first reacted with a diisocyanate to form the polyurethane prepolymer, together with a subsequent crosslinking reaction with a diamine and/or with water, in particular only with water. In this connection, a “two-bath concept” is also presented as a method of treating the tensile member as part of an upstream processing stage. The tensile member is dipped into a mixture of a polyurethane prepolymer and an inert solvent/dispersant, the voids in the tensile member becoming at least partially filled with this mixture. This is followed by a drying operation. Finally a crosslinking reaction with water is carried out. This is followed by the manufacture of the belt using the tensile member thus treated.
The belt body itself may consist of a different material, although the preference is again for using a crosslinked polyurethane which, however, may have a different composition than the polyurethane for the tensile member treatment.